Parasites are selfish, and so am I
A nice thing about writing a monthly nature blog is that in any month there are a gagillion topics to write about. At times it can be hard to pick just one thing to focus on. And so, often I find myself with two, three, or even four stories cooking at once.
Every now and then a topic comes out of nowhere—a topic so hot and heavy that it’s one I simply cannot ignore. Take the mushroom scene of September 2021, it was insane, and all the cool summer bug stuff had to take a back seat to the fungus. And rightly so.
The focus of this month’s Nature Bummin’ sort of happened this way. This topic has been really in my in my face recently and it seems to be everywhere I look. In a way, it’s been in my face (and probably yours) for years. There is some magic in this, because the topic also falls into the “how have I not seen this before?” category. This kind of duality—to be in your face for years & to not have been seen before makes for a special treasure that doesn’t turn up just any old day. And here’s the real kicker—it’s a friggin’ plant!
Witches’ Broom – “Wiccaphobic” or “Wiggedy Wack”
As I said before, this topic is one that simply can’t be ignored any longer. It must be written about and shouted about at the tops of our lungs, “witches’ broom!” Okay, here’s a quick PSA on witches’ broom.
PSA – It should be stated that not all witches carry, fly, or ever even sweep with brooms. This is what we call in the business a stereotype. Harry Potter got just as much wrong as he got right, if not more, but that’s not relevant. “Witches’ broom” offends those who identify as witches and who wouldn’t be caught dead (or alive or whatever) with such a domestic cleaning device in hand, much less riding one. The term “witches’ broom” also reinforcing the belief that we should associate brooms with witches… as if all witches and ONLY witches use brooms!
The same goes for the shrubby plant thing called “Witch-hazel” named because its flowers look like warts with hairs growing out of them. There are plenty of non-witches that have hairy warts. Wiccaphobic and exclusive. Not cool Botanists, not cool.
Okay, now that this PSA is out of my system, what were we talking about again?
You are probably thinking, “Kirk you are writing about plants, what gives?” Well, if you look back at the old Nature Bummin’s (and be my guest) you will see that every now and then plants are honorably mentioned, often with a connection to an animal that uses them, but still, they often get a shout out. And if you really think about it, plants are technically part of nature, so, they have their moments… maybe not as frequently as members of the other Kingdoms have them. Regardless, they’re having a moment now.
You might also be thinking “Wait, witches’ broom? Are you talking about a growth formation?” Yes, and yes. Witches’ brooms are cool and funky and not all that uncommon in Spruce Maritime forests along the coast, but they still are just a plant growth formation. I hope we’ve all experienced the brooms enough to recognize them. See photo if not.
What if I were to tell you that these growths are more than just the tree’s way of stirring up the cultural divide between witches and non-witches? (Well Duh!) I mean the brooms are clearly part of the spruce tree—just look, you can see the needles. Still, there are a variety of reasons why a plant might have such a broomish growth, and none relate to witchcraft at all!
While witches’ broom can grow in a variety of trees and shrubs (pine, fir, and heck even high bush blueberry for Pete’s sake!), the most common species I find these formations on are white and red spruce trees. As it appears, these growths happen to be fairly common in spruces along the coast. I cross paths with them on almost every preserve I visit. The main instigator for the broomish formation in spruces goes by the name Arceuthobium pusillum. Those in the know, might know this plant as eastern dwarf mistletoe. If you’re familiar with the coast, you are likely familiar with this species too.
God bless the parasites.
When it comes to plants, I am a sucker for those we refer to as “parasitic”. Many of my favorite Maine plants are parasitic and have completely given up on Chlorophyll, they say “no to photosynthesis”. Instead, they parasitizing a trees’ roots (or more likely parasitize a fungus that happens to be mychorrizhal with the tree). These have fun names like – Ghost Pipes, Beech Drops, and Pine Sap.
Eastern Dwarf Mistletoe doesn’t completely shun photosynthesis, but it’s way more parasitic than not.
I first learned of dwarf mistletoe and witches’ brooms in 2001 when my wife and I lived and worked in Haines, Alaska. What I knew then was to tell folks on hikes that the brooms were caused mostly by a species of dwarf mistletoe and that the flowers were really tiny. Like really tiny.
When we moved to Vinalhaven in 2004 we saw the brooms and figured it was the same dwarf mistletoe. So much about coastal Maine reminds me of Alaska, witches’ brooms included. I didn’t know of course then that it was a different species of dwarf mistletoe altogether, but how would I?
Before we get too far ahead of ourselves, let’s talk some…
“Dwarf mistletoe is a parasitic plant that lives its entire life within the canopy of the tree.”
Mistletoe life cycle basics, what has been in our faces all along
“Dwarf mistletoe is a parasitic plant that lives its entire life within the canopy of the tree.”
— University of Minnesota
Wow, thanks University of Minnesota! Do plants usually move between habitats? Anyway, you won’t find it growing on the ground, I think that is the point here. Sweet and simple.
“Eastern Dwarf Mistletoe, a parasitic plant that stimulates the production of large twiggy growths (brooms) on native spruce, is common in some stands of white and red spruce on islands and headlands along the Maine coast.”
Ahh, there you have it.
“Eastern dwarf mistletoe is a hemiparasitic plant which grows inside the stems of a host plant. Once a seed lands on a branch it will germinate and grow a haustorium which penetrates past the cambium layer and into the host’s xylem and phloem tissues; from those tissues it gathers nutrients needed for its own growth and reproduction.”
— Wikipedia (so it must be true).
It’s not just a parasitic plant—it’s a ‘hemi’—which means it’s a parasitic plant. The haustorium is a thin projection from the root of the parasitic plant, that allows the plant to penetrate its host and steal its’ nutrients. So, that’s how they get into a Spruce.
Here’s more from the Department of Agriculture…
“Seeds germinate in the spring. A structure called a radicle emerges from a germinating seed and grows along the bark surface and penetrates the host tissue. The mistletoe’s endophytic system then develops in the bark and wood of the host. Infection occurs most readily in 1- to 5-year-old twigs because their bark is more easily penetrated than older twigs.”
Wait, radicle? I thought it was a Haustorium? What’s the diff? Well, it ends up the radicle is the first part of a mistletoe seedling that emerges from said seed(ling) during the process of germination. Haustorium are specialized cells on the radicle that are used to penetrate the plant. There you have it totally radicle.
“In general, haustorial cells occupy intercellular spaces and displace the host tissue, but enzymes also digest the host cell walls. Once a parasitic plant has encountered a host, it must penetrate the cambium and establish an interface. The interface is extremely varied. In most cases, the parasite forms a continuum with the xylem of the host plant, but in others (e.g., Cuscuta), the parasitic plant taps into the phloem.”
Whoa, enzymes to digest cell walls? Man, how is this not the state flower of Maine? Back to the Department of Agriculture discussion of Eastern Dwarf Mistletoe…
“For two or more years, these infections are quiescent, or latent, and there are no symptoms. The first symptom is a swelling at the point of infection. Buds proliferate at this point, giving arse to a witches’ broom, a compact mass of branches and twigs. Initial growth of witches’ broom may be quite vigorous.”
That tiny little plant, or better yet several in the same tree, can eventually weaken and kill the tree.
It certainly can be vigorous in growth! The compact witches’ broom increases the sugar producing photosynthesis in the infected tree, but the nutrients obtained through this process go to the dwarf mistletoe rather than the tree itself. That tiny little plant, or better yet several in the same tree, can eventually weaken and kill the tree.
Mistletoe life cycle basics… How have I never seen that before?
Here’s what’s new (for me) this spring – back to the Department of Agriculture
“Aerial shoots typically appear four years after infection, and these produce flowers and fruits in their fifth year. Thus, plants need at least five years to complete their life cycle from initial establishment to dissemination of their first seed crop. Many successive crops of aerial shoots may be produced from the established endophytic system.”
An endophyte “lives within a plant for at least part of its life cycle without causing apparent disease.” The key part there is “part of its life cycle” not causing disease. Here’s more…
“…they obtain most of their nutrients from the living tissue of the host through what is called the endophytic system. This root-like network consists of cortical strands growing within the bark and sinkers within the wood. The endophytic system lives as long as adjacent host tissues are alive.”
So, the mistletoe spreads within the infected branch causing little to no harm, and once established (after a couple years) goes off with witches’ broom and then sends up aerial shoots from this established system.
So, this is what I have been observing over the last month or more!
“…green to brown external (aerial) shoots, usually no secondary branching, and leaves reduced in size to small scales… The major function of the shoots is reproduction. Male and female flowers are small and produced on separate plants.”
Plants are male or female so there is no chance of self-pollination. We like that. Some call it
dioecious, and those some would be correct.
Is that Dwarf Mistletoe or are you glad to see me?
So, my friend John and I were working in the woods on Vinalhaven in March when noticed aerial shoots on a spruce limb we were going to cut down (and burn) but in the end we decided to leave it. Neither of us had seen what turned out to be Dwarf Mistletoe aerial shoots before, and we were curious to see how they developed. Over the next few weeks, Male Dwarf Mistletoe flowers bloomed here—the first either of us had ever seen—and they continue to bloom as of this writing. It was—and don’t tell anyone—kind of exciting.
I found aerial shoots just about everywhere.
I was ready to go back to this particular spruce limb to watch the changes, but it ended up I didn’t need to. I found aerial shoots just about everywhere. At every Vinalhaven and St George peninsula preserve, as well as on any Midcoast island I visited (and more).
And the best part is that these weren’t minuscule flowers way up high in the canopy. No, they were eye level and poppin’ on (what seemed) every spruce twig and branch. Finally, Dwarf Mistletoe flower was checked off my bucket list.
Mistletoe life cycle basics – what’s coming up….
Okay – so this has been fun and all, but there must be more…
After the female flowers are pollinated, they develop fruits like all good plants do. Then the fun begins…
“Fruits mature in August or September of the same year they were pollinated. Each mature fruit contains one seed about 0.1 inches (3mm) in length. The seeds are discharged explosively from ripe fruits at this time. They may travel as far as 55 ft, but most land within 10-15 feet of the disseminating shoot.”
Heck yeah and this is what I want to see! Dwarf mistletoe fireworks! A show of seeds shooting in each and every direction… I could finally practice my Matrix dodging skills with them. Wouldn’t that be something? It made me wonder how long one would have to stay to see this, what conditions are best. Only one way to find out…
Side note, while there are undoubtedly lots of plants that shoot their seeds (so to speak), the one I’ve heard of in Northeast North America other than dwarf mistletoe is witch hazel, the plant mentioned in the PSA early. Maybe they use the word “witch” because the seeds fly. Anyway, witch plants unite!
“A sticky seed coating called viscin enables seeds to stick to objects they strike. Foliage is the most common receiving surface. Seeds also can stick to the bodies of birds and squirrels as they forage in infected trees. Animals can inadvertently carry seeds to trees farther away than by natural discharge, potentially starting new infection centers.”
I want to be a mistletoe seed disperser! Sign me up please! Wonder how hard it is to get out of beards…
“Viscin, when first moistened by rains, acts as a lubricant. Seeds slide down and either fall off needles or become lodged on bark at the base of needles. Seeds are fastened in place when the viscin dries and they overwinter in a dormant state… Seeds germinate in spring.”
And it starts all over again! With the radicles and haustoriums and such. Lot going on here.
What the future entails is told by the present?
It goes to show, that you don’t ever know what you might find in the woods. I remember working in Alaska and a co-worker told a group that she had been leading hikes there for three years and still was finding new stuff. I thought that was a funny statement but didn’t tell her so. I mean, can you ever really see everything? Heck, I’ve been exploring woods in Maine for 20 years and there are still tons of stuff right in front of me that I’ve never seen. And in the case of dwarf mistletoe there’s stuff that I have seen for forever (witches’ brooms) and still haven’t really seen.
That’s why I love it so much when anyone says, “you missed it!” about an occurrence or sighting in nature. “No spraint” is my new response, “I miss a million things everyday”. But that doesn’t make me stop looking. Nope, I will never stop looking…
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